# JOHANNES KEPLER (1571 - 1630). "Strena seu de Nive Sexangula>" in *Amphitheatrum Sapientiae Socraticae Joco-seriae*, Caspar Dornau, ed. Hanau: Daniel and David Aubrii & Clementis Schleichius, 1619.

One of the great geniuses of humanity, Kepler became an adherent of the heliocentric theory of planetary motion first developed by the Polish astronomer Nicolaus Copernicus (1473 - 1543). Kepler held the chair of astronomy and mathematics at the University of Graz, Austria, from 1594 until 1600, when he became assistant to the Danish astronomer Tycho Brahe (1546 - 1601) in the latter's observatory near Prague. On Brahe's death, Kepler assumed his position as imperial mathematician and court astronomer, and in 1612 Kepler became mathematician to the states of Upper Austria.

Kepler's Strena Seu de Nive Sexangula is the first scientific treatise concerning crystallography. This small tract, written in the form of a letter, was presented as a new year's gift to a patron. In it, Kepler pondered the problem of why snowflakes are always six-sided. But every explanation the author formulated, he also rejected, and eventually Kepler concluded that the true explanation remained for future investigators to resolve. The crystallographic importance of this work arises from the author's discussions of space filling and symmetry. Published here for the first time are Kepler's discussions of how ordered symmetrical shapes arise from the packing together of similar bodies, even though the bodies are not symmetric themselves. Included in these observations are accounts of cubic and hexagonal closest packing, an important concept of modern crystallographic studies.

The 1611 pamphlet is extremely rare; only about a dozen copies are present in North American libraries. Shown here is a reprinting of Kepler's text published in 1619 in a book edited by one of Kepler's friends, the German physician Casper Dornau (1577 - 1632). This book, one of the largest and most fascinating collections of the period, contains almost 700 works including comic treatises, poems, observations on animals, plants, and minerals; biographies of personages of antiquity, and discussions of such things as injustice, folly, fever, gout, and envy. Kepler's treatise on the snowflake is reprinted in this collected work, volume I, pp. 751-757.

Schuh, Curtis P. *Mineralogy & Crystallography: An Annotated Bibliography of Books Published 1469 through 1919*. Tucson: privately published, 2005, p832.